Condenser motor



Inventor: Wayne JMorriH,

w. J. MORRILL CONDENSER MOTOR Filed Nov. 4, 1 932 Dec. 3, 1935.

Patented D... 3, 1935 am: Wayne .LhlarrlILI'artWayneJndaa-Igncrto'General New York fleets-lo Company.

corporation s am November 4. ms. saw so. sum

roam. (cam-m) II. The switch open, which is the running condition. I

My invention relates to alternating current condenser motors of thesingle phase split phase type, and in particular to an improvedand-simplifled scheme ior varying the amount oi! capacitance betweenstarting and running conditions. The primary object 011 my'invention isto provide low cost condenser motor equipment with simplecontrolgmechanism in which capacitance is employed both for starting andfor power iactor-correotion during running while utilising the condenserequipment to the best advantage with- ,out subjecting to over-voltage,at the same time obtaining a high ratio of change in capacitance betweenstarting and running conditions. 7 n

i -In carrying my invention into eflect, I employ a plurality ofcondensers or capacitance groups for connection in parallel and seriesrelation under starting and running conditions. By making the number ofsuch groups odd, such as 3 or 5,

' I am able to employ relatively simple and in- A expensive switchingequipment and avoid the necessity of carryin any or the motor circuitsthrough switch contacts during the running period or the motor, withtheexception oi. the line 6 switch contacts.

i The features 01 my invention which are lie- 11 iieved 'to be novel andpatentable will be pointed out in the claim appended hereto. For abetter understanding of the invention, reference is made 0 insthgfollowing description to the accomp nying drawing, showing in Fig. .1 anarrangement employing three equal condensersor capacitance groups whichare connected-in parallel at start and in series for running, giving aratio of nine to one; Fig. Z'represents a modification where one or thecondensers has a larger capacitythan the other two andis short-circuitedfor running purposes, giving a'ratio in the example given of ten" toone; and Rig. 3' represents the useot five cal0 pacitance groups forobtaining a capacitance ratio oi twenty-five to one between starting andrunning conditions.

In Fig. 1, I have shown a usual form of split. phase motor, with theexception 01 the condenser 45 uipmeht. The main winding is representedat and the'starting winding at H. A rotor sec-' ondary or the squirrelcage variety isrepresented at It. The line connectionsat I3 contain thej'usuallineswitchll. I 50 Permanently connected in series relationwiththe starting winding are the condensers II, It and I1, and this circuitis permanently connected in parallel with the mainwinding it. at I! is aspeed responsive device for operating a doubleas pole single mow switchhaving bases "and is shown withboth contacts;

To those familiar with the-operation of appa- Cratusotthischaracteritwillbeappreciated that the arrangementiustdescribed is a highly de 5 ble one, since during the normal runningperiod 0! the motor there is no current flowing through movable contactpoints in the" control circuits. -v 'r" f when starting period, thespeed responsive switch is closed, and in this position the threecondensers in parallelin the startins'winding are circuit, Thus,condenser II is connected across conductors 2i and 22 through blade is,condenser i1 is connected across" the same conductors through blade II,and condenser i6 is connected across conductors ii and 23 through bothblades ll and It. switch blades carry onlyltwothirds of the startingcurrent, while the other'20 one-third is carried through the permanentcon ncctions to the terminal condensers. The direction of current flowat a given instant isrepresented by the arrows, and the number 0! headsin each arrow" represent the relative current mag 25 nitudes in thecircuits during the starting connection. This gives aratio bicapacitance of 9 to 1 between starting. and rimning' conditions. Thus,under normal running conditions no current is carried through thecontacts of the con-' trol switch, while during". the short starting peariod only a portion oi the-current is carried therethrough. -In bothconnections the permanent connections are utilizedlbut not disturbed.Inthis form of motor, the capacitance volt 3 amperes should beappreciably greater at start than during On the other hand, the voltageacross the entire condenser equipment rises considerably betweenstarting and running conditions, due to'the rise in voltage across the40 r starting winding,'and this can be controlled somewhat by desismasby changin the resistance or the squirrel cage and the relative numberof turns in thegmain and starting windings oi the motor.

To use the condenser equipment most efliciently, 2

the voltage across a given condenser should not be in excess 0! itsrated voltage during continuous operation, since too high a voltageunder these conditions produces undue heat and short liiefw 0n the otherhand, if the condenser equipment is run considerably below its ratedvoltage, it results inan uneconomical use or the condenser, equipment.the short starting period it is advantageous to" use a higher .thanrated voltage across a given condenser, since during this the motorisatrest. aiid during them a short period this will do no harm and saves inthe condenser costs.

The above statement applies to the modern paper type of condenser. Ifacondenser be of the electrolytic type it should not be operated atother than approximately the rated voltage. Operation of an electrolyticcondenser at too low a voltage results.in the deformation of the film,which reduces its eificiency and useful life at normal voltage. Ingeneral, the electrolytic type of condenser is not suitable forcontinuous operation, but conditions arise where it is advantageous touse sucha condenser during the starting period.

I consider that by means of my invention I am able to more nearlyapproach the correct change in capacitance ratio, while maintaining amore nearly desirable voltage relationacross each condenser betweenstarting and running conditions, without sacrifice in motor design, thanhas been possible with previous schemes for solving this complicatedproblem. Heretofore, the capacitance ratio between starting and runningconditions has been appreciably less. I

In Fig. 2, the motor is similar to that shown in Fig. 1, but thecondenser equipment is modified to obtain a ratio between starting andrunning conditions of ten to one. Here condensers 23 and 24 have asmaller capacity than condenser 25. To give an example, condensers 23and 24 may be each of microfarads capacity, and condenser of 60microfarads capacity. The latter which is used only at start may be ofthe electrolytic type. At start, the condensers are connected inparallel in the starting winding circuit,

as inFig. 1, when the control switch blades is and 20 are thrown to theright on contacts '26 and 2.1, at which time we have '100 micro-faradscapacity in the starting winding circuit.

For running; the control switch is in the position shown, condenser 25is short-circuited through switch blade l9 and contact 28 whilecondensers23 and 24 are connected in series with the starting windingthrough the same control circuit. The permanent'series connections arenot disturbed. Now the capacity in the starting winding circuit isdetermined by the smaller condensers connected in series, giving a ratioof 10 to 1 between these two conditions. By an economical design of themotor the voltage relation across the condenser equipment betweenstarting and running conditions may be made about in the ratio of 110m180, so that with 110 volts across the condensers at start we have 180volts across condensers 23 and 24 in series, or 90 volts across, eachduring running. This illustrates the flexibility oi the scheme to obtaindifferent ratios windings, an odd number of condensers greatercondensers having a greater'capacitance than while maintainingapproximately rated voltage across the condensers in use during startingand running conditions without unduly complicating the control switch.It will be appreciated that by changing the relative value of thecapacitance 5 of condenser 25 with respect to that of condensers 23 and24 in Fig. 2, we may obtain a wide variety of capacitance ratios betweenstarting andrunning conditions. Thus by making condensers 23, 24, and 25of 20, 20 and 110 microfarads capacity, respectively, the capacitance atstart is their sum, or 150, and for running it is half of one of theseriesconnected condensers, or 10, or a ratio of 15 to 1.

If it is desired to go to am higher ratios, we 15 approach the pointwhere it will be desirable to go to.the arrangement shown in Fig. 3,using five equal condensers to 34, inclusive, in parallel at start andin series for running, giving a ratio of 25 to 1. During normal runningthe permanent connection shown with the control switch opened is used,there being no control circuit carried through any switch contact. Withswitch 35 closed, the condensers are connected in parallel, four-fifthsof the current in the starting winding circuit going through the controlswitch, and theother one-fifth going through the permanent connectionsto the end condensers, as indicated by the arrows.

From the above it is seen that by the use of an odd number of condensersa wide variety of capacitance ratios may'be had with very simple controlmechanism, and that for certain ratios we obtain the advantage ofpermanent connections during running conditions and a reduction 35 instarting current through the switch contacts at starting. These sameadvantages cannot be obtained with the use of an even number ofcondensers.

Such other modifications of my invention as 40 will occur to those.skilled in the art are intended to be included within the scope of theappended claim.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

A condenser. motor having main and'starting than one, means permanentlyconnecting said condensers in series relationwith the starting Ywinding, and the series connection thus formed in parallel with the mainwinding, one of said the, other two, and means for connecting saidcondensers in multiple for starting the motor andshort-circuitingthelarger condenser for running 5 conditions. I WAYNE JMORRJLL.

